The Laws of War: Their Nature and Moral Function

In his final address on issues of war and peace, President Obama reminds us all that “[w]e are a nation that stands for the rule of law, and strengthen[s] the laws of war.” But what is the nature of the laws of war, and what moral function do they serve? Do the laws of war constitute the exclusive legal and moral framework for the use of deadly force in armed conflict? Or do the laws of war apply alongside other legal and moral norms, each offering distinct protections from violence and abuse?

In two recent posts, I argued that the laws of war limit and constrain the use of deadly force, but do not authorize or justify the use of deadly force contrary to other applicable legal rules. In particular, I argued that international humanitarian law (IHL) applies alongside international human rights law (IHRL), which may place additional constraints on the use of deadly force. What I left unsaid, among other things, is that IHL exhausts neither the legal constraints nor the moral constraints applicable during armed conflict.

Responding over on Opinio Juris, Charles Kels—a major in the U.S. Air Force writing in his personal capacity—elegantly expresses the opposing view. Charles ascribes IHL’s “moral force” to its status “as a self-contained system of licenses and limitations” that exhausts a combatant’s legal and moral obligations. Charles describes IHL as “a specially-defined space wherein soldiers can act effectively, decisively, justly, and—yes—violently pursuant to a unique code of conduct.” On this view, IHL must apply to the exclusion of other legal and moral constraints in order for IHL to perform its legal and moral function.

In this post, I will argue that the view that Charles presents, though attractive to many, is both false and dangerous. Since I discuss the nature and moral function of IHL at some length in my forthcoming book, I will try to limit myself to those points most relevant to the current debate.

IHL: One Set of Rules Among Others

As Charles observes, I take the view that “that IHL does not authorize conduct which it fails to prohibit: comportment with IHL is a necessary, but not sufficient, condition of lawful killing in armed conflict.” Charles seems to reject this view, going so far as to describe IHL as “a self-contained system of licenses and limitations.” I respectfully disagree.

As an Air Force officer, Charles must accept that IHL does not authorize conduct which it fails to prohibit. After all, a pilot who carries out an airstrike unauthorized by his or her commanding officer would surely face a court martial even if the airstrike does not violate IHL. Similarly, Charles must accept that comportment with IHL is a necessary, but not sufficient, condition of lawful killing in armed conflict. After all, a soldier who violates rules of engagement more restrictive than IHL would similarly face a court martial.

This is enough to show that IHL is not, in fact, “a self-contained system of licenses and limitations.” IHL applies alongside other legal rules applicable to the conduct of armed conflict. State armed forces must consider and comply with all applicable legal rules, not only IHL. It is the job of military lawyers to distill these applicable legal rules into rules of engagement that ordinary soldiers can understand and apply on the battlefield.

One might respond that IHL authorizes conduct under international law which it fails to prohibit and, similarly, that comportment with IHL is a sufficient condition of lawful killing in armed conflict under international law. Such a response would be mistaken.

For example, a first use of armed force between States may violate the jus ad bellum—the law governing the resort to armed force—but not the jus in bello—the law governing the conduct of hostilities. Such a use of force would not be authorized under international law but would instead be prohibited under international law. Certainly, international law cannot authorize and prohibit the same act at the same time. Accordingly, the same act cannot be authorized by IHL and prohibited by the jus ad bellum. Such a view would introduce incoherence into the very heart of the jus belli regime. This is enough to show that “comportment with IHL is a necessary, but not sufficient, condition of lawful killing in armed conflict” under international law.

Returning to the topic of my earlier posts, if States may adopt legal rules more restrictive than IHL through domestic legislation or standing rules of engagement then surely States may also adopt legal rules more restrictive than IHL by ratifying an IHRL treaty that applies during armed conflict. As I have argued, that is exactly what States have done.

During armed conflict, the specific rules of IHL provide more detailed guidance to fighters than the general prohibition of arbitrary killing in IHRL. Nevertheless, the general prohibition retains independent content. By way of analogy, the specific rules of driving (speed limits, turn signals, etc) provide more detailed guidance to drivers than the general prohibition of reckless driving. Nevertheless, driving that violates no specific rule may still be reckless.

In response, Charles asks “is a speed limit of 75 miles per hour not, at least in some way, permission to drive 70?” No, it is not. A speed limit of 75 miles per hour is not a permission to drive without a license (authorization) or while intoxicated (parallel constraint). In non-international armed conflict, legal authorization to fight comes from domestic law, while both domestic law and IHRL impose parallel constraints. In international armed conflict, legal authorization to fight ultimately derives from the jus ad bellum.

Combatant Immunity: A Limited Bar to Domestic Prosecution

Charles seems to agree with me “that IHL does not confer ‘affirmative’ legal authorities on states.” However, Charles insists that IHL “does privilege and immunize certain conduct that would otherwise be illegal.” In particular, Charles writes that IHL “removes the presumption that killing is unlawful in virtually all cases besides self-defense.” Quoting Telford Taylor, Charles writes that “[w]ar consists largely of acts that would be criminal if performed in time of peace.”

With respect, this is not correct. Combatant immunity is a carefully limited rule of international law that prohibits the criminal prosecution of lawful combatants by an adversary State for conduct that violates the domestic criminal law of that adversary State but does not also violate IHL. Combatant immunity simply has no bearing on a soldier’s legal obligations under the domestic law of his or her own State or under international law.

As we have seen, combatant immunity does not relieve soldiers of their domestic legal obligations to obey rules of engagement that are more restrictive than IHL. Nor would combatant immunity relieve soldiers of their legal obligations under otherwise applicable IHRL treaties that their State has ratified.

To see that combatant immunity does not affect obligations under international law, consider a senior military commander “in a position effectively to exercise control over or to direct the . . . military action of a State” who plans, prepares, initiates, or executes a use of armed force against another State that manifestly violates the jus ad bellum. As a lawful combatant, such a commander would enjoy combatant immunity from prosecution under the domestic criminal law of the victim State so long as the use of armed force does not violate IHL. Nevertheless, such a commander may be prosecuted under international law for the crime of aggression.

To sum up, State armed forces whose conduct does not violate IHL may violate (i) the domestic law of the adversary State, (ii) the domestic law of their own State, or (iii) other rules of international law. Combatant immunity offers a limited bar to prosecution only for violations of (i), that is, for violations of the domestic law of the adversary State.

As Charles notes, I take the view that “combatant immunity is inapplicable in NIACs,” for two reasons. First, most States are unwilling to extending combatant immunity to armed groups. Second, State armed forces do not need combatant immunity from the law of NIAC. Thus, there is no reason to compromise the core principle that IHL applies equally to opposing parties.

In internal NIACs, immunity (indeed, authorization) for State armed forces comes from domestic law, not from IHL. In cross-border NIACs with the consent of the host State, immunity for intervening forces comes from the domestic law of the host State (often alongside a status of forces agreement). In cross-border NIACs without the consent of the host State, immunity for intervening forces comes from the law of IAC. As Charles knows, I take the view (following Dapo Akande and the ICRC) that the use of force by one State on the territory of another State without its consent triggers an IAC between the two States (see here, here, here, and here). Accordingly, members of the intervening force would enjoy combatant immunity from prosecution under the domestic law of the territorial State. Thus, there is no need for the law of NIAC to confer combatant immunity on State armed force, let alone on armed groups, or compromise the equal application of IHL.

The Moral Function of IHL

Charles and I agree that IHL serves an important moral function. However, we seem to disagree, in interesting ways, about the nature of that moral function. Charles describes IHL as “a moral lodestar critical to defining what it means to be an honorable warrior” and as “a specially-defined space wherein soldiers can act effectively, decisively, justly, and—yes—violently pursuant to a unique code of conduct.” Taken literally, these passages suggest that IHL defines what is morally permissible in war. On this view, conformity with IHL guarantees conformity with moral norms.

Since this view seems quite implausible, Charles probably meant to assert a weaker claim. After all, IHL has developed over time, could have developed quite differently than it did, and remains an appropriate object of moral criticism. For example, terror bombing cities was never morally permissible, even if it was once (or could have been) not prohibited by IHL. Similarly, the fact that IHL does not prohibit killing sleeping or unarmed combatants who could easily be captured hardly entails that such killings are morally permissible.

Perhaps Charles meant to assert the weaker claim that IHL aspires or purports to guarantee moral permissibility in war. However, IHL cannot guarantee moral permissibility because IHL applies equally to States fighting unjust wars of aggression and to States fighting just wars of national self-defense. Accordingly, IHL can only sensibly aspire or sincerely purport to guarantee moral permissibility in partnership with the jus ad bellum, sharing a moral division of labor.

Certainly, the senior military commander who directs an aggressive use of interstate force acts impermissibly, even if the use of force conforms to IHL. After all, the only thing morally worse than killing other human beings for no good reason is killing other human beings for bad reasons.

What of the ordinary soldiers who carry out an aggressive use of force? Here we must distinguish between the moral permissibility of an act and the moral blameworthiness of an actor. If an aggressive use of force is morally impermissible then the ordinary soldiers who carry it out act impermissibly. Their professional obligations and oath of service cannot override the moral prohibition on killing—particularly collaterally killing civilians—in pursuit of an unjust cause. At the same time, it may be unjust to blame or punish ordinary soldiers for fighting in an unjust war authorized by their government. It is for this reason, among others, that ordinary soldiers can neither commit nor be held complicit in the crime of aggression.

Nevertheless, it seems impossible to deny that soldiers take a grave moral risk when they vow to fight in wars that may prove unjust—because there is no just cause for resorting to war, or because an otherwise just cause could be achieved without resorting to war, or because an otherwise just cause is not sufficiently important to justify the harm that would be inflicted in its pursuit. For this reason, among others, those of us who still live in democracies have a moral responsibility to our soldiers, among others, to ensure that our governments do not send our soldiers to fight, die, and kill for an unjust cause.

IHL and IHRL (Again)

Of course, in my view, both IHL and the jus ad bellum share this moral division of labor with IHRL, sound rules of engagement, and moral considerations that resist legal codification. Together, these varied sources of normative guidance may very well guarantee moral permissibility in war. However, in my view, IHL alone can only promise that soldiers will come closer to conforming to their moral obligations if they follow IHL than if they violate IHL. This would, itself, constitute an important moral achievement. It is a promise worth keeping.

As Charles notes, I take the view that State armed forces may violate IHRL by killing members of organized armed groups whom they could safely capture. Charles objects that this view will have “the practical effect of undermining clarity in status-based targeting.” Yet, as Charles well knows, State armed forces routinely receive rules of engagement, tactical directives, and specific orders not to kill fighters whom they can safely capture. Indeed, IHL may itself prohibit killing fighters whom one could safely capture if killing those fighters would endanger nearby civilians. So my view cannot be dismissed as impractical. If my view is correct, then State armed forces are more than capable of implementing it.

Killing opposing combatants whom one could safely capture does not violate IHL, but it violates both IHRL and basic moral norms. If we tell soldiers that such killing is morally permissible because it is not prohibited by IHL, then they may act “effectively” and “decisively.” However, they will not act “justly.” Telling them otherwise may be a noble lie, meant to spare them the painful truth that IHL alone will not guarantee that they will return home without moral blemish. But it is a lie all the same.